Membrane structure and MEMS piezoelectric microphone using the same

Abstract

The application provides a MEMS structure and a MEMS piezoelectric microphone using the same. The MEMS structure comprises: a substrate comprising: a peripheral substrate outer ring body; a substrate back cavity formed on the inner side of the substrate outer ring body; a composite layer formed on the substrate, which comprises in the horizontal direction: a peripheral layer formed above the substrate outer ring body; a vibration layer formed on the inner side of the peripheral layer and above the substrate back cavity; and a stress release structure comprising: N arc-shaped hollow slits passing through the vibration layer, N >= 3; wherein the inner ends of the N arc-shaped hollow slits are uniformly distributed on a central circle with the center of the vibration layer as the center and R as the radius, R > 0. In the application, compared with straight-line slits or other structures, the residual stress release effect of the arc-shaped hollow slits is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of micro-electro-mechanical systems (MEMS), and more particularly to a MEMS structure and a MEMS piezoelectric microphone using the same. Background Technology

[0002] MEMS microphones mainly include two types: condenser and piezoelectric. MEMS piezoelectric microphones are microphones fabricated using microelectromechanical systems (MEMS) technology and piezoelectric thin film technology. Due to the use of semiconductor planar processing and bulk silicon fabrication techniques, they are small in size, compact, and highly consistent. Compared to condenser microphones, they also have advantages such as not requiring a bias voltage, a wider operating temperature range, and dust and water resistance. However, their lower sensitivity and signal-to-noise ratio limit the development of MEMS piezoelectric microphones.

[0003] Residual stress is one of the main reasons for low sensitivity. Currently, the most effective method to release residual stress is to design the piezoelectric composite resonator as a cantilever structure, which effectively releases residual stress through the expansion and contraction of the free boundary. However, cantilever structures have disadvantages such as poor stability, inconsistent low-frequency response, and severe low-frequency sound leakage. A four-sided fixed structure can effectively overcome these disadvantages, but there is currently no effective method to release residual stress within the structure. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In order to at least partially solve one of the above-mentioned technical problems, the present invention provides a MEMS structure and a MEMS piezoelectric microphone using the same.

[0006] (II) Technical Solution

[0007] In a first aspect, the present invention provides a MEMS structure. The MEMS structure includes: a substrate, comprising: an outer ring body surrounding the substrate; a substrate back cavity formed inside the outer ring body; a composite layer formed on the substrate, which in the horizontal direction includes: an outer layer formed above the outer ring body; a vibration layer formed inside the outer layer and above the substrate back cavity; and a stress relief structure, comprising: N arc-shaped perforated slits penetrating the vibration layer, N≥3; wherein the inner ends of the N arc-shaped perforated slits are uniformly distributed on a central circle with radius R centered on the center of the vibration layer, R>0.

[0008] In some embodiments of the present invention, the arc-shaped hollow slit is tangent to the central circle.

[0009] In some embodiments of the present invention, the horizontal cross-section of the vibration layer is circular, wherein: the N arc-shaped perforated slits have the same radius, the same orientation, and the same or regularly varying length; and / or the outer starting point of the arc-shaped perforated slits is located at the edge of the vibration layer; and / or the center of the arc-shaped perforated slits is located at the edge of the vibration layer; and / or the inner end of the arc-shaped perforated slits, the center of the vibration layer, and the center of the arc-shaped perforated slits are collinear.

[0010] In some embodiments of the present invention, the width of the arc-shaped perforated slit is between 0.5 μm and 5 μm.

[0011] In some embodiments of the present invention, the MEMS structure includes: M groups of stress relief structures, M≥2; the central circles corresponding to the M groups of stress relief structures are concentric.

[0012] In some embodiments of the present invention, the MEMS structure is a dual-electrode structure, and the composite layer includes, in the vertical direction: a support layer formed on a substrate; a lower electrode layer, a piezoelectric layer, and an upper electrode layer formed sequentially on the support layer.

[0013] In some embodiments of the present invention, the horizontal cross-section of the upper electrode layer is circular and formed inside the central circle, and the arc-shaped hollow slit penetrates the piezoelectric layer, the lower electrode layer and the support layer.

[0014] In some embodiments of the present invention, the horizontal cross-sections of the upper electrode layer, the piezoelectric layer, and the lower electrode layer are circular, and the three are formed inside the central circle; the arc-shaped hollow slit penetrates the support layer.

[0015] In some embodiments of the present invention, the horizontal cross-section of the upper electrode layer is annular and formed on the outside of the central circle; the inner part of the arc-shaped hollow slit penetrates the piezoelectric layer, the lower electrode layer, and the support layer, and the outer part penetrates the upper electrode layer, the piezoelectric layer, the lower electrode layer, and the support layer.

[0016] In some embodiments of the present invention, the horizontal cross-section of the upper electrode layer, the piezoelectric layer, and the lower electrode layer is annular, and the three are formed outside the central circle; the inner part of the arc-shaped hollow slit penetrates the support layer, and the outer part penetrates the upper electrode layer, the piezoelectric layer, the lower electrode layer, and the support layer.

[0017] In some embodiments of the present invention, the MEMS structure is a three-electrode structure, and the composite layer includes, in the vertical direction: a first piezoelectric layer, a middle electrode layer, and a second piezoelectric layer, which are formed sequentially on the substrate; a lower electrode layer is formed below the first piezoelectric layer, and an upper electrode layer is formed above the second piezoelectric layer.

[0018] In some embodiments of the present invention, the horizontal cross-sections of the upper electrode layer and the lower electrode layer are circular, formed inside the central circle, and their projections on the horizontal cross-sections completely overlap; the arc-shaped hollow slit penetrates the second piezoelectric layer, the middle electrode layer, and the first piezoelectric layer.

[0019] In some embodiments of the present invention, the horizontal cross-sections of the upper electrode layer and the lower electrode layer are annular, formed on the outside of the central circle, and their projections on the horizontal cross-sections completely overlap; the inner part of the arc-shaped hollow slit penetrates the second piezoelectric layer, the middle electrode layer, and the first piezoelectric layer, and the outer part penetrates the upper electrode layer, the second piezoelectric layer, the middle electrode layer, the first piezoelectric layer, and the lower electrode layer.

[0020] In some embodiments of the present invention, the vibration layer is circular in the horizontal direction.

[0021] In some embodiments of the present invention, the horizontal cross-sections of the upper electrode layer and the lower electrode layer are circular and formed inside the central circle, and the radial extension length of the arc-shaped hollow slit is less than 50% of the radius of the vibration layer.

[0022] In some embodiments of the present invention, the horizontal cross-sections of the upper electrode layer and the lower electrode layer are annular and formed outside the central circle, and the radial extension length of the arc-shaped hollow slit is greater than 50% of the radius of the vibration layer.

[0023] In some embodiments of the present invention, the radius of the vibration layer is between 0.1 mm and 3 mm.

[0024] In some embodiments of the present invention, the material of the support layer is selected from one or more of the following: silicon, silicon nitride, silicon oxide, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

[0025] In some embodiments of the present invention, the materials of the piezoelectric layer, the first piezoelectric layer, and the second piezoelectric layer are selected from one or more of the following: aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and piezoelectric ceramics, and their thickness is between 0.1 μm and 10 μm.

[0026] In some embodiments of the present invention, the materials of the lower electrode layer, the middle electrode layer, and the upper electrode layer are selected from one or more of the following: molybdenum, gold, aluminum, and chromium, and their thickness is between 20nm and 200nm.

[0027] In some embodiments of the present invention, the MEMS structure is a dual-electrode structure.

[0028] In some embodiments of the present invention, the horizontal cross-sections of the upper electrode layer, the piezoelectric layer, and the lower electrode layer are circular, and the three are formed inside the central circle; the arc-shaped hollow slit penetrates the support layer; the outer edges of the upper electrode layer, the piezoelectric layer, and the lower electrode layer are flush; the material of the support layer is silicon nitride; the material of the upper electrode layer and the lower electrode layer is aluminum; and the material of the piezoelectric layer is zinc oxide.

[0029] In a second aspect, a MEMS piezoelectric microphone is provided. The MEMS piezoelectric microphone includes the MEMS structure described above.

[0030] (III) Beneficial Effects

[0031] As can be seen from the above technical solution, the present invention has at least one of the following beneficial effects compared to the prior art:

[0032] (1) N arc-shaped perforated slits are set through the vibration layer, and these N arc-shaped perforated slits are evenly distributed on a central circle with the center of the vibration layer as the center and radius R as the radius. Compared with straight slits or other structures, the residual stress release effect of arc-shaped perforated slits is significantly improved. At the same time, the arc-shaped perforated slits can also avoid the pressure difference between the back acoustic cavity and the front acoustic cavity during the packaging process, thereby improving the reliability of the MEMS structure.

[0033] (2) N arc-shaped perforated slits are tangent to the same central circle. Since all arc-shaped perforated slits are tangent to the central circle, when there is residual stress in the structure, the residual stress can be released by rotating the central circle at a small angle to deform the entire MEMS structure, thereby improving sensitivity.

[0034] (3) The outer starting point and center of the N arc-shaped hollow slits are located at the edge of the vibration layer, which makes it more effective for releasing residual stress.

[0035] (4) The MEMS structure of the present invention can be applied to two-electrode and three-electrode structures, and has strong adaptability.

[0036] (5) Simulation results show that the MEMS structure provided by the present invention can significantly release residual stress to reduce the resonant frequency, thereby helping to improve the sensitivity of the microphone. Attached Figure Description

[0037] Figures 1-3 These are, respectively, a perspective view, a top view, and a cross-sectional view (AA section) of the first embodiment of the MEMS structure of the present invention.

[0038] Figure 4 , Figure 5 These are, respectively, a perspective view and a cross-sectional view of the second embodiment of the MEMS structure of the present invention.

[0039] Figure 6 For residual stress pairs Figure 4 The influence of the MEMS structure shown and the comparative structure on the resonant frequency is illustrated.

[0040] Figure 7 , Figure 8 , Figure 9 These are, respectively, a perspective view, a top view, and a cross-sectional view (AA section) of the third embodiment of the MEMS structure of the present invention.

[0041] Figure 10 for Figures 7-9The simulation displacement cloud diagram shows the MEMS structure releasing residual tensile stress through in-plane rotation.

[0042] Figure 11 , Figure 12 These are, respectively, a perspective view and a cross-sectional view of the fourth embodiment of the MEMS structure of the present invention. Detailed Implementation

[0043] This invention proposes a four-sided fixed MEMS structure with an arc-shaped hollow slit to achieve better stress release.

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0045] Before describing the solution to the problem, it is helpful to define some specific terms. In this document, according to the common understanding of those skilled in the art, "inner" refers to the direction closer to the center of the vibrating layer, and "outer" refers to the direction farther from the center of the vibrating layer; "upper" refers to the direction vertically from the substrate towards the composite layer, and "lower" refers to the direction vertically from the composite layer towards the substrate. Of course, those skilled in the art should also understand that these directions are only relative.

[0046] According to a first aspect of the present invention, a MEMS structure is provided.

[0047] Figures 1-3 These are, respectively, a perspective view, a top view, and an AA cross-sectional view of the first embodiment of the MEMS structure of the present invention. Please refer to... Figures 1-3 The MEMS structure in this embodiment includes:

[0048] Substrate 10;

[0049] Composite layer 20 formed on substrate;

[0050] The stress relief structure 30 formed on the composite layer includes: N arc-shaped perforated slits penetrating the vibration layer, where N≥3.

[0051] In this embodiment, compared to straight slits or other structures, the arc-shaped perforated slit has a significantly improved residual stress release capability. Simultaneously, the arc-shaped perforated slit can also prevent pressure differences between the back acoustic cavity and the front acoustic cavity during the encapsulation process, improving the reliability of the MEMS structure.

[0052] The following section provides a detailed description of each part of the MEMS structure in this embodiment.

[0053] The substrate 10 includes: an outer ring body 11 on the periphery of the substrate; and a back cavity 12 formed inside the outer ring body of the substrate.

[0054] In this embodiment, the MEMS structure is a dual-electrode structure, and the composite layer 20 is formed on the substrate 10. In the vertical direction, it includes: a support layer 21a, formed on the substrate; a lower electrode layer 21b, a piezoelectric layer 21c, and an upper electrode layer 21d, which are sequentially formed on the support layer.

[0055] The support layer 21a can be made of silicon (Si), silicon nitride (Si3N4), silicon oxide (SiO2), or various piezoelectric materials. The piezoelectric layer 21c can be made of aluminum nitride (AlN), scandium-doped aluminum nitride (Sc), or other similar materials. x Al 1-x Materials such as nitrogen (N), zinc oxide (ZnO), and piezoelectric ceramics (lead zirconate titanate, PZT) are preferred, with a thickness range of 0.1 μm to 10 μm. The materials for the lower electrode layer 21b and the upper electrode layer 21d can be molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), etc., with a preferred thickness range of 20 nm to 200 nm. The radius of the upper electrode layer 21d is determined by the maximum output energy.

[0056] In the horizontal direction, the composite layer 20 includes: a peripheral layer 22a formed above the outer ring of the substrate; and a vibration layer 22b formed inside the peripheral layer and above the substrate back cavity. In this embodiment, the horizontal cross-section of the substrate back cavity 12 is circular, therefore the horizontal cross-section of the vibration layer 22b is also circular. Preferably, the radius R of the vibration layer is... V The range is 0.1mm-3mm.

[0057] The stress relief structure 30 includes N arc-shaped perforated slits penetrating the vibrating layer, where N ≥ 3. The specific value of N is determined based on the bandwidth required for the microphone design. The width of the arc-shaped perforated slits is between 0.5 μm and 5 μm. A width less than 5 μm prevents low-frequency sound leakage. The N arc-shaped perforated slits are evenly distributed circumferentially along the vibrating layer, extending inward from the edge of the vibrating layer, with their inner ends tangent to the same central circle. Figure 2 In the diagram, the dashed circle 40 represents the central circle tangent to the arc-shaped perforated slit. This central circle is concentric with the vibrating layer.

[0058] The applicant discovered that while in-plane expansion and contraction of cantilever structures can release residual stress, for structures fixed at all four sides, in-plane tensile or compressive deformation is required to release residual stress. However, typical through-holes or slits cannot allow for effective in-plane deformation of the entire membrane. In the case of the MEMS structure fixed at all four sides in this embodiment, when the arc-shaped slit is tangent to the central circle, regardless of whether the entire membrane is under tensile or compressive stress, the entire structure can be deformed by rotating the central circle at a small angle clockwise or counterclockwise, thereby releasing residual stress and improving the sensitivity of the MEMS structure.

[0059] Specifically, in this embodiment, the vibrating layer has a radius of 500 μm, a central circle radius of 480 μm, and a piezoelectric layer radius of 410 μm. The vibrating layer is 800 nm thick silicon nitride, the electrode layer is 100 nm thick aluminum, and the piezoelectric layer is 800 nm thick zinc oxide. The vibrating layer edge has 18 arc-shaped perforated slits, each 3 μm wide.

[0060] Please refer to Figure 2 The central dot is the center of the vibration layer. It can be seen that the inner end of the arc-shaped perforated slit, the center of the vibration layer, and the center of the arc-shaped perforated slit are collinear. In this embodiment, the outer starting point and center of the arc-shaped perforated slit are both located at the edge of the vibration layer, thus making the release of residual stress more effective.

[0061] Please refer to Figures 1-3 The upper electrode layer 21d has a circular horizontal cross-section and is formed inside the central circle. The stress relief structure 30 penetrates the piezoelectric layer 21c, the lower electrode layer 21b, and the support layer 21a.

[0062] Regarding stress relief structures, the following five points need to be explained:

[0063] (1) The arc-shaped hollow slit is tangent to the central circle.

[0064] Since all the arc-shaped openwork slits are tangent to the central circle, when there is residual stress in the structure, the central circle can drive the entire structure to rotate, thereby effectively releasing the residual stress and improving sensitivity.

[0065] Of course, the invention can also be achieved if the arc-shaped hollow slit is not tangent to the central circle, but its effect will not be as good as the structure of this embodiment.

[0066] (2) The center of the arc-shaped hollow slit

[0067] In this embodiment, the center of the arc-shaped perforated slit is located at the edge of the vibration layer, but the present invention is not limited thereto. In other embodiments of the present invention, the center of the arc-shaped perforated slit may not be located at the edge of the vibration layer, for example, at a predetermined distance from the edge of the vibration layer, and the present invention can still be achieved, but its effect will not be as good as the structure of this embodiment.

[0068] (3) The outer starting point of the arc-shaped hollow slit

[0069] In this embodiment, the outer starting points of the N arc-shaped perforated slits are located at the edge of the vibration layer. In other embodiments of the present invention, the outer starting points of the N arc-shaped perforated slits may also be at a distance from the edge of the vibration layer, for example, 0.5 mm to 1 mm.

[0070] (4) Length of a single arc-shaped perforated slit

[0071] In this embodiment, the length of the arc-shaped perforated slit is less than 10% of the radius of the vibration layer. For MEMS structures that output electrical signals using a central circular electrode, preferably, the radial extension length of the arc-shaped perforated slit is less than 50% of the radius of the vibration layer. For MEMS structures that output electrical signals using a ring electrode, preferably, the radial extension length of the arc-shaped perforated slit is greater than 50% of the radius of the vibration layer. In other words, the longer the radial extension length of the arc-shaped perforated slit, the greater the deformation of the vibration layer. However, its length is also constrained by multiple factors such as the electrical signal output method, and needs to be considered comprehensively.

[0072] (5) Length of the arc-shaped openwork slit

[0073] In this embodiment, the N arc-shaped perforated slits are of the same length, but the invention is not limited thereto. In other embodiments of the invention, the arc-shaped perforated slits may also exhibit regular variations, such as one long and one short, or one long and two short. However, the deformation of the entire vibration layer depends on the longest arc-shaped perforated slit; therefore, having N arc-shaped perforated slits of the same length achieves the best technical effect.

[0074] (6) Number of stress relief structures

[0075] In this embodiment, a set of stress relief structures is provided, but the invention is not limited thereto. In other embodiments of the invention, there may be M sets of stress relief structures on the vibration layer, namely M sets of arc-shaped hollow slits, with each set of arc-shaped hollow slits corresponding to its own central circle. The central circles corresponding to the M sets of arc-shaped hollow slits are concentric but have different radii.

[0076] (7) Width of the arc-shaped openwork slit

[0077] In this document, "slit" is a narrow gap as commonly understood by those skilled in the art. Preferably, the width of the arc-shaped perforated slit is between 0.5 μm and 5 μm, but the present invention is not limited thereto. In other embodiments of the present invention, the width of the slit may be less than 100 μm.

[0078] It should be noted that after introducing the specific details of the MEMS structure, those skilled in the art, based on their professional knowledge, should easily conceive of how to fabricate and prepare the aforementioned MEMS structure. Therefore, this article will not provide further detailed explanations of the fabrication methods for the above-mentioned MEMS structures.

[0079] Figure 4 , Figure 5 These are, respectively, a perspective view and a cross-sectional view of the second embodiment of the MEMS structure of the present invention. The MEMS structure of this embodiment is similar to... Figures 1-3The difference in the MEMS structure shown is that the horizontal cross-section of the upper electrode layer 21d, the piezoelectric layer 21c, and the lower electrode layer 21b is circular, and the three are formed inside the central circle; the arc-shaped hollow slit penetrates the support layer 21a.

[0080] In this embodiment, the edges of the piezoelectric layer are partially etched. At this point, the diameter of the piezoelectric layer is smaller than the diameter of the central circle, which effectively prevents the cancellation of positive and negative stresses within the piezoelectric layer. Simultaneously, the partial etching of the edge piezoelectric layer effectively releases the bending stiffness of the composite layer, thereby increasing the vibration displacement of the composite layer and improving its sensitivity.

[0081] Figure 6 For residual stress pairs Figure 4 The influence of structural resonant frequency. Residual stress affects the bending stiffness of a structure, which in turn directly affects the resonant frequency. Therefore, the ability of a structure to release residual stress can be compared by observing the resonant frequency. The comparison structures are those of the same size and material without slit elements. It can be seen that the embodiments of the present invention can significantly release residual stress to reduce the resonant frequency, thereby helping to improve sensitivity.

[0082] Figure 7 , Figure 8 , Figure 9 These are, respectively, a perspective view, a top view, and a cross-sectional view (AA section) of the third embodiment of the MEMS structure of the present invention. The MEMS structure of this embodiment is... Figures 1-3 The difference in the MEMS structure shown is that the horizontal cross-section of the upper electrode layer 21d is annular and formed on the outside of the central circle; the inner part of the arc-shaped hollow slit penetrates the piezoelectric layer 21c, the lower electrode layer 21b, and the support layer 21a, while the outer part penetrates the upper electrode layer, the piezoelectric layer, the lower electrode layer, and the support layer.

[0083] In this embodiment, the arc-shaped hollow slit extends further into the interior of the composite vibration layer, and the maximum stress during structural vibration will gradually be distributed to the edge of the composite vibration layer. At this time, the original central circular electrode is changed to the edge ring electrode.

[0084] Figure 10 for Figures 7-9 The simulation displacement cloud diagrams of the MEMS structure shown demonstrate the release of residual tensile stress through in-plane rotation. (a) and (b) show the displacement cloud diagrams of the MEMS structure before and after stress release, respectively. It can be seen that when residual tensile stress exists in the structure, because the arc-shaped slit is tangent to the central circle, the tensile stress causes the central circle to rotate slightly clockwise, thus deforming the entire MEMS structure and effectively releasing the residual stress, which helps improve the structure's sensitivity. Similarly, when residual compressive stress exists in the structure, the central circle will rotate slightly counterclockwise, causing the entire MEMS structure to deform, thus effectively releasing the residual stress, reducing the resonant frequency, and improving the structure's sensitivity.

[0085] Figure 11 , Figure 12 These are a three-dimensional and cross-sectional view of the MEMS structure according to the fourth embodiment of the present invention. This embodiment further etches the piezoelectric layer in the central region based on the third embodiment. Specifically, the horizontal cross-section of the upper electrode layer 21d, piezoelectric layer 21c, and lower electrode layer 21b is annular, and all three are formed outside the central circle; the inner portion of the arc-shaped perforated slit penetrates the support layer 21a, and the outer portion penetrates the upper electrode layer 21d, piezoelectric layer 21c, lower electrode layer 21b, and support layer 21a. This embodiment helps to further reduce the structural bending stiffness to increase vibration displacement, thereby improving sensitivity.

[0086] The MEMS structures in the above four embodiments all adopt a dual-electrode structure, that is, using an upper electrode and a lower electrode to output signals. However, the technical solution of the present invention can also be applied to a three-electrode structure.

[0087] In a fifth exemplary embodiment of the present invention, a MEMS structure employing a three-electrode structure is provided. In this MEMS structure, the composite layer vertically comprises: a first piezoelectric layer, a middle electrode layer, and a second piezoelectric layer, all three formed sequentially on the substrate; a lower electrode layer is formed below the first piezoelectric layer; and an upper electrode layer is formed above the second piezoelectric layer. Figure 1 The MEMS structure shown is similar, with the upper and lower electrode layers having circular horizontal cross-sections formed inside the central circle, and their projections on the horizontal cross-sections completely coinciding. An arc-shaped perforated slit penetrates the second piezoelectric layer, the middle electrode layer, and the first piezoelectric layer. This embodiment has similar beneficial effects to the first embodiment, which will not be repeated here.

[0088] In a sixth exemplary embodiment of the present invention, a MEMS structure employing a three-electrode structure is provided. The difference between this embodiment and the fifth embodiment is that, in this embodiment, the horizontal cross-sections of the upper and lower electrode layers are annular, formed outside the central circle, and their projections on the horizontal cross-section completely overlap; the inner portion of the arc-shaped perforated slit penetrates the second piezoelectric layer, the middle electrode layer, and the first piezoelectric layer, while the outer portion penetrates the upper electrode layer, the second piezoelectric layer, the middle electrode layer, the first piezoelectric layer, and the lower electrode layer. This embodiment has similar beneficial effects to the third embodiment, which will not be repeated here.

[0089] According to a second aspect of the present invention, a MEMS piezoelectric microphone is also provided. The MEMS piezoelectric microphone includes a MEMS structure as described in any of the six embodiments above. Detailed information regarding the MEMS structure can be found in the prior description and will not be repeated here. Detailed information regarding the MEMS piezoelectric microphone can be found in the relevant descriptions of the prior art, and will also not be repeated here.

[0090] This concludes the description of the various embodiments of the present invention. Based on the above description, those skilled in the art should have a clear understanding of the present invention.

[0091] It should be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," "right," "inner," and "outer," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of the present invention. Throughout the accompanying drawings, the same elements are represented by the same or similar reference numerals. Furthermore, the shapes and dimensions of the components in the drawings do not reflect their actual size and proportions, but are only intended to illustrate the content of the embodiments of the present invention.

[0092] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0093] Unless explicitly stated otherwise, the numerical parameters in the specification and claims of this invention may be approximate values ​​and may be changed according to the content of this invention. Specifically, all figures in the specification and claims indicating the content of composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases, which means that they include a specific amount varying by ±10% in some embodiments.

[0094] Those skilled in the art will understand that in the claims and specification of this invention, the word "comprising" does not exclude the presence of elements (or steps) not listed in the claims. The word "a" or "an" preceding an element (or step) does not exclude the presence of a plurality of such elements (or steps).

[0095] For certain implementations, if they are not key aspects of the present invention and are well-known to those skilled in the art, they have not been described in detail in the accompanying drawings or text due to space limitations. In such cases, reference can be made to relevant prior art for understanding. Furthermore, the purpose of providing the above embodiments is merely to ensure that the present invention meets legal requirements. The present invention can be implemented in many different forms and should not be construed as limited to the embodiments described herein. Moreover, the above definitions of elements and methods are not limited to the various specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can make simple modifications or substitutions.

[0096] Similarly, it should be understood that, for the sake of brevity, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of invention should not be construed as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, the various inventive aspects consist of fewer than all the features of the preceding single embodiment. Furthermore, embodiments may be used in combination with each other or with other embodiments based on design and reliability considerations; that is, technical features from different embodiments can be freely combined to form more embodiments. Therefore, the claims following the detailed description are hereby expressly incorporated into this detailed description, wherein each claim itself is a separate embodiment of the invention.

[0097] The above specific embodiments have provided a detailed description of the purpose, technical means, and beneficial effects of the present invention. It should be understood that the purpose of the detailed description is to enable those skilled in the art to better understand the present invention, and it is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A MEMS structure, characterized in that, include: The substrate includes: an outer ring body of the substrate on the periphery; and a substrate back cavity formed inside the outer ring body of the substrate. A composite layer is formed on the substrate, which includes, in the horizontal direction: a peripheral layer formed above the outer ring of the substrate; and a vibration layer formed inside the peripheral layer and above the back cavity of the substrate. The stress relief structure includes: N arc-shaped perforated slits penetrating the vibration layer, where N ≥ 3; the inner ends of the N arc-shaped perforated slits are evenly distributed on a central circle with radius R centered on the center of the vibration layer, where R > 0; the arc-shaped perforated slits are tangent to the central circle; the inner ends of the arc-shaped perforated slits, the center of the vibration layer, and the center of the arc-shaped perforated slits are collinear; The horizontal cross-section of the vibration layer is circular, and the N arc-shaped perforated slits have the same radius, the same orientation, and the same length; the outer starting point of the arc-shaped perforated slits is located at the edge of the vibration layer; the center of the arc-shaped perforated slits is located at the edge of the vibration layer. When residual stress exists in the structure, it can be released by rotating the central circle at a small angle to deform the entire MEMS structure.

2. The MEMS structure according to claim 1, characterized in that, The width of the arc-shaped hollow slit is between 0.5μm and 5μm; and / or The MEMS structure includes: M sets of stress relief structures, where M ≥ 2; The central circles corresponding to the stress relief structures in group M are concentric.

3. The MEMS structure according to claim 1, characterized in that, The MEMS structure is a dual-electrode structure, and the composite layer includes, in the vertical direction: a support layer formed on the substrate; a lower electrode layer, a piezoelectric layer, and an upper electrode layer formed sequentially on the support layer; wherein: The upper electrode layer has a circular horizontal cross-section, formed inside the central circle, and the arc-shaped perforated slit penetrates the piezoelectric layer, the lower electrode layer, and the support layer; or The upper electrode layer, piezoelectric layer, and lower electrode layer have circular horizontal cross-sections, and are formed inside the central circle; the arc-shaped perforated slit penetrates the support layer; or The horizontal cross-section of the upper electrode layer is annular, formed outside the central circle; the inner portion of the arc-shaped perforated slit penetrates the piezoelectric layer, the lower electrode layer, and the support layer, while the outer portion penetrates the upper electrode layer, the piezoelectric layer, the lower electrode layer, and the support layer; or The horizontal cross-section of the upper electrode layer, piezoelectric layer, and lower electrode layer is annular, and the three are formed outside the central circle; the inner part of the arc-shaped hollow slit penetrates the support layer, and the outer part penetrates the upper electrode layer, piezoelectric layer, lower electrode layer, and support layer.

4. The MEMS structure according to claim 1, characterized in that, The MEMS structure is a three-electrode structure. The composite layer includes, in the vertical direction: a first piezoelectric layer, a middle electrode layer, and a second piezoelectric layer, which are sequentially formed on the substrate; a lower electrode layer is formed below the first piezoelectric layer, and an upper electrode layer is formed above the second piezoelectric layer, wherein: The upper and lower electrode layers have circular horizontal cross-sections, formed inside the central circle, and their projections on the horizontal cross-sections completely overlap; the arc-shaped perforated slit penetrates the second piezoelectric layer, the middle electrode layer, and the first piezoelectric layer; or The horizontal cross-sections of the upper electrode layer and the lower electrode layer are annular, formed on the outside of the central circle, and their projections on the horizontal cross-sections completely overlap; the inner part of the arc-shaped hollow slit penetrates the second piezoelectric layer, the middle electrode layer, and the first piezoelectric layer, while the outer part penetrates the upper electrode layer, the second piezoelectric layer, the middle electrode layer, the first piezoelectric layer, and the lower electrode layer.

5. The MEMS structure according to claim 3 or 4, characterized in that, The vibrating layer is circular in the horizontal direction, wherein: The upper and lower electrode layers have circular horizontal cross-sections, formed inside the central circle, and the radial extension length of the arc-shaped perforated slit is less than 50% of the radius of the vibration layer; and / or The horizontal cross-sections of the upper and lower electrode layers are annular and formed outside the central circle. The radial extension length of the arc-shaped perforated slit is greater than 50% of the radius of the vibration layer.

6. The MEMS structure according to claim 3 or 4, characterized in that, The radius of the vibration layer is between 0.1 mm and 3 mm.

7. The MEMS structure according to claim 3, characterized in that, The material of the support layer is selected from one or more of the following: silicon, silicon nitride, silicon oxide, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lead zirconate titanate; and / or The material of the piezoelectric layer is selected from one or more of the following: aluminum nitride, scandium-doped aluminum nitride, zinc oxide, piezoelectric ceramics, and its thickness is between 0.1 μm and 10 μm.

8. The MEMS structure according to claim 4, characterized in that, The materials of the first piezoelectric layer and the second piezoelectric layer are selected from one or more of the following: aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and piezoelectric ceramics, and their thickness is between 0.1 μm and 10 μm; and / or The materials of the lower electrode layer, middle electrode layer, and upper electrode layer are selected from one or more of the following: molybdenum, gold, aluminum, and chromium, and their thickness is between 20nm and 200nm.

9. The MEMS structure according to claim 7, characterized in that, The upper electrode layer, piezoelectric layer, and lower electrode layer have circular horizontal cross-sections and are formed inside the central circle; the arc-shaped hollow slit penetrates the support layer; The outer edges of the upper electrode layer, piezoelectric layer, and lower electrode layer are flush. The material of the support layer is silicon nitride, the material of the upper electrode layer and the lower electrode layer is aluminum, and the material of the piezoelectric layer is zinc oxide.

10. A MEMS piezoelectric microphone, characterized in that, include: The MEMS structure as described in any one of claims 1 to 4.

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